Lupus anticoagulant (LA) was evaluated using a three-step procedure according to the guidelines of The International Society of Thrombosis and Haemostasis [31 ]. To clarify, dilute Russell’s viper venom time (dRVVT; LA1-screen; Siemens, Germany) and a sensitive aPTT (PTT LA; Diagnostica Stago, France) were used for screening, whereas LA2-confirm (Siemens, Germany) and Staclot LA (Diagnostica Stago, USA) were run to affirm the result. Levels of anticardiolipin (ACL) and anti-β2-glycoprotein I (Aβ2GPI) antibodies, IgM and IgG classes, were performed with commercially available immunoenzymatic assays (QUANTA Lite® aCL and aβ2GPI (Inova Diagnostics, San Diego, USA)).
Ptt la
Manufactured by Diagnostica Stago
Sourced in France
The PTT LA is a laboratory instrument used to measure the activated partial thromboplastin time (aPTT) in blood samples. The aPTT test is a common coagulation assay that helps assess the intrinsic and common pathways of the blood clotting process.
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Lab products found in correlation
Staclot la, by Diagnostica Stago (4 mentions)
La1 screen, by Siemens (2 mentions)
La2 confirm, by Siemens (2 mentions)
Actin fsl, by Siemens (1 mentions)
Sta neoptimal, by Diagnostica Stago (1 mentions)
Sta r evolution analyzer, by Diagnostica Stago (1 mentions)
Sta liquid anti xa, by Diagnostica Stago (1 mentions)
Sta ptt automate, by Diagnostica Stago (1 mentions)
Hemoclot thrombin inhibitors, by Hyphen Biomed (1 mentions)
6 protocols using ptt la
1
Lupus Anticoagulant Evaluation Protocol
2
Lupus Anticoagulant Detection Assay
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Lupus anticoagulant (LA) was determined in a three-step procedure according to the guidelines of The International Society of Thrombosis and Haemostasis, as described elsewhere [13] (link). Briefly, diluted Russell's viper venom time (dRVVT; LA1-screen; Siemens, Germany) and a sensitive aPTT (PTT LA; Diagnostica Stago, France) were used for screening, whereas LA2-confirm (Siemens, Germany) and Staclot LA (Diagnostica Stago, USA) were run for the confirmation. Reference values for each test were established using 99th percentile of the healthy population. Commercially available immunoenzymatic assays were applied to determine anticardiolipin (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibodies (QUANTA Lite® aCL and aβ2GPI (Inova Diagnostics, San Diego, USA)).
3
Lupus Anticoagulant Diagnosis Protocol
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LA was diagnosed according to the recommendations of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis [18 (link), 19 (link)] and as described [16 (link)]. Two different screening tests including a lupus-sensitive activated partial thromboplastin time (PTT-LA, Diagnostica Stago, Asnières-sur-Seine, France) and a diluted Russell viper venom time were used for LA determination. For patients who received vitamin K antagonists (VKAs) as anticoagulation, only aPTT was used for screening. As soon as one or both screening tests were prolonged, further analysis and confirmatory tests were performed on these samples, as described elsewhere [20 (link)].
Patients, whose LA confirmatory tests were not clearly positive but had a Rosner index (calculated as 100 × (clotting times of the 1:1 mixture − normal plasma)/patient’s plasma) value above 15, were still considered LA positive [21 (link)]. The StaClot LA (Diagnostica Stago, Asnières-sur-Seine, France) and the dRVVT-LA confirm (Life Diagnostics, Clarkston, GA, USA) were used as confirmatory assay.
Patients, whose LA confirmatory tests were not clearly positive but had a Rosner index (calculated as 100 × (clotting times of the 1:1 mixture − normal plasma)/patient’s plasma) value above 15, were still considered LA positive [21 (link)]. The StaClot LA (Diagnostica Stago, Asnières-sur-Seine, France) and the dRVVT-LA confirm (Life Diagnostics, Clarkston, GA, USA) were used as confirmatory assay.
4
Lupus Anticoagulant Screening Protocol
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For the LA screening, the aPTT test (PTT LA; Diagnostica STAGO, Asnieres, France) and the dRVVT test (DVVtest®10, American Diagnostica Inc., Stamford, USA) were performed according to the manufacturers' guidelines. A value more than two standard deviations above the mean reference level was considered positive. Since our present study included APL assay results obtained from 2007 to 2009 and the ISTH 2009 recommendations were not established at that time, the revised LA guidelines (2009) regarding the generation of LA assay cut-off value were not applied in this study [6 (link)].
5
Comparative Evaluation of Clotting Reagents
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APTT reagents used included Triniclot S, PTT-LA (Diagnostica Stago, Asnières-sur-Seine, France), Cephen 5 (lupus anticoagulant resistant, Hyphen BioMed, France), Hemosil Synthasil (IL/Werfen, San Diego, CA, USA), Actin FSL (Siemens, Forchheim, Germany), and Intrinsin LR (Haematex, HTX). All were used with 3 min activation times and 0.025 M calcium chloride for recalcification.
Prothrombin time (PT) reagents included PT Phen (HBM) and Neoptimal (Stago).
Dilute Russell viper venom time (dRVVT) reagents included Staclot DRVV-Screen and Confirm (Stago), Hemoclot LA-S (HBM) and Go-DOAC Test (DCT, HTX). Go DOAC is a dRVV-based clotting reagent modified for higher sensitivity to all DOACs.
All clotting tests were carried out in duplicate in Stago ST4 instruments using 50 µL plasma samples and 100 µL of PT reagents, or 50 µL of dRVVT reagents, or 50 µL APTT reagents followed by 50 µL 0.025 M calcium chloride.
Prothrombin time (PT) reagents included PT Phen (HBM) and Neoptimal (Stago).
Dilute Russell viper venom time (dRVVT) reagents included Staclot DRVV-Screen and Confirm (Stago), Hemoclot LA-S (HBM) and Go-DOAC Test (DCT, HTX). Go DOAC is a dRVV-based clotting reagent modified for higher sensitivity to all DOACs.
All clotting tests were carried out in duplicate in Stago ST4 instruments using 50 µL plasma samples and 100 µL of PT reagents, or 50 µL of dRVVT reagents, or 50 µL APTT reagents followed by 50 µL 0.025 M calcium chloride.
6
Coagulation Assays for Anticoagulant Monitoring
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LAC testing was performed according to the ISTH guidelines by a three‐step (screening‐mixing‐confirmatory) method using a dRVVT‐ and aPTT‐based test system,14 using STA‐Staclot dRVV Screen, STA‐Staclot dRVV Confirm, PTT‐LA, and Staclot LA reagents (Diagnostica Stago), as previously described.37 Results are expressed as normalized clotting ratio (NCR) or a difference of CT for Staclot LA aPTT.14 , 37 Apixaban, rivaroxaban, and edoxaban levels were measured using a chromogenic anti‐Xa assay (STA‐Liquid anti‐Xa; Diagnostica Stago) calibrated for the corresponding DOAC. A diluted thrombin time (TT) assay (Hemoclot Thrombin Inhibitors, Hyphen BioMed) was used for measurement of dabigatran concentrations. Routine coagulation parameters, PT and aPTT, were determined using STA‐NeoPtimal and STA‐PTT Automate (Diagnostica Stago), respectively. Heparins were measured by a chromogenic anti‐Xa assay (STA‐Liquid anti‐Xa, Diagnostica Stago). Intrinsic and extrinsic coagulation factors were measured by one‐stage assays using STA‐(immuno)deficient plasma and C.K. Prest or STA‐NeoPtimal, respectively. All analyses were performed on a STA‐R Evolution analyzer (Diagnostica Stago).
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